Simple, powerful, demonstrable: Meyer Burger on why HJT is poised for the mainstream

Interview: Following the announcement earlier this month that Swiss production equipment supplier Meyer Burger has increased the power output of its HJT SmartWire module to 335W, pv magazine caught up with company CTO, Gunter Erfurt to understand more about the process, as well as the company’s longer-term tech roadmap.

Meyer Burger CTO Gunter Erfurt at the company's technology day earlier this month.

Image: Meyer Burger

pv magazine: Meyer Burger has recently achieved 335 Watts (W) power output on a module deploying its heterojunction (HJT) cell and SmartWire (SWCT) interconnection technologies. What is the significance of the milestone?

Gunter Erfurt: This is a very important milestone for Meyer Burger for many reasons. It is an outstanding result having achieved 335 W power on a 60-cell glass-white backsheet module. Moreover, it is important because we were using standard M2 n-type wafers that are readily available in the market. Sometimes champion modules that are promoted in the market contain many elements which will seldom make it into mass manufacturing or do not contribute to increased energy yields under standard conditions.

At Meyer Burger, we want to demonstrate solutions capable for mass manufacturing. The result we published with best efficiency of 24.02% on the cell side has been confirmed by Fraunhofer ISE, who carefully reviewed our IV measurements and the calibration behind the technique. We also took the module, which we flashed in Thun at 335 W to TÜV Rheinland and they too confirmed the measurement.

Do you hold the view that high efficiency technological advances are the best way to continue driving down solar costs?

We strongly believe that providing production solutions for highly efficient solar cells has a major impact on driving down solar energy costs. The supply chain element in manufacturing is the other important factor. With higher cell efficiencies, manufacturers drive down the specific wafer costs per watt peak, and of course the cost per module. The other important characteristic of HJT is the energy yield, which enables superior LCOE. Data that we have continuously harvested from global site installations for more than a year show that the HJT modules not only exhibit these very high efficiencies and powers, but also a much better energy yield compared to any other module technology. This reduces LCOE and also increases the value proposition of HJT for EPC and utility companies.

We now have live, long term data from HJT installations globally, and the message and feedback received from third parties is that compared to a standard monofacial reference, our modules exhibit up to 30% more energy yield and up to 15% more energy yield than PERT and PERC bifacial modules at the same power installed respectively. This is what we expected from our simulations, and now we have the proof.

Apart from the 335 W module, we see that with our HELiA product line for HJT solar cells combined with SWCT for module connection, we can enable our customers to operate cell and module manufacturing at 320 W average module power. This is a major achievement because HJT modules and solar cells manufactured on Meyer Burger machinery enable those customers and manufacturers to produce high power at the same low cost structure as current PERC modules, but you get 20 W more on average. When you review all products currently available, you find that the average PERC power is around 300 W in the industry today.

This additional 20 W of power makes a big difference if we compare today’s HJT status with today’s PERC status. To take PERC to the same power level is definitely possible, but it won’t happen tomorrow and it will add process complexity and eventually require additional upgrades on existing lines. In our opinion, for any new installations, HJT is becoming the focus because the power is already there, and the production process itself is very slim, with only six process steps required and continuous improvement possible.

The gap between today’s 300 W average for PERC and 320 W for Meyer Burger’s HJT/SWCT module will remain – we are convinced of this. The technology roadmap for continued improvement is already in place, and has been worked on by Meyer Burger together with customers who have already installed lines.

How long will it take until 335 W becomes the industry average?

When we look at the pace of evolutionary power increase for existing technologies, what we find – and what has been published – is between 5-8 W increases per year for a 60-cell module. This has been the trend, and is likely to continue to be so for the next few years. Achieving 335 W on average will be a topic for the next 18 months. The nice thing about HJT is that while Meyer Burger has strong knowledge about solar cells, I am 100% certain that leading solar companies manufacturing cells and modules could, if they adopt this technology, drive power increases much faster than an equipment manufacturer like Meyer Burger.

That being said, there is a high likelihood that efficiency and power increases for the new HJT and SWCT interconnection technology will be much faster than for technologies like PERC and PERT where smaller incremental steps need to be applied.

What is your view on HJT’s future market adoption growth? ITRPV roadmap puts HJT’s share of the cell market at 10% by 2026 – would you suggest it could be, in fact, higher?

At our recent technology day we forecasted HJT to be at 15 GW in 2021, assuming the growth of the sector until then continues at the current rate. When you review the ITRPV from 2015, when PERC was becoming more and more attractive, we see that the PERC forecast was only 50% of what the market today actually is. The PERC upgrade technology was there at the right moment, at the right cost, and at the right maturity level for the manufacturing equipment that needed to be incorporated into the lines, and that really pushed the PERC case much faster than what the industry expected. There is a chance that the same could happen with HJT, or an even faster adoption rate.

The ITRPV forecast has PERC dominating, which is also good for Meyer Burger of course. But we believe that the additional power increase for PERC – while technically feasible – will not be possible by simply utilizing the existing PERC process of an aluminium oxide layer on the cell backside.

That means that complexity of the advanced PERC process will increase, which may positively trigger HJT’s adoption rates because if advanced PERC becomes too complex, companies that are planning further expansion might consider a process sequence that is much simpler. A process that uses only six steps, requiring a smaller footprint and less facility utility complexity, e.g. just one wet bench instead of two or three in the line as well as a low temperature process, which is ready today to use for wafer thicknesses of <150 µm and that of course means HJT and SWCT. We are also seeing a trend towards using LCOE as the main solar key performance indicator instead of a pure dollar per watt peak metric and there HJT has a clear advantage because of the superior energy yield at low manufacturing costs.

How does HJT/SWCT compete on cost when compared to another high efficiency combination like mono PERC and multi busbar?

It is a favorable comparison. We have live existing data from the production line at Meyer Burger that allows us to calculate step costs for the process. We can say that today – also confirmed by major solar manufacturers – that Opex for HJT is very competitive with today’s PERC Opex cost. When you look at the volume in place for PERC, and the ongoing demand: this is not yet the case with HJT, which shows how vast the potential is. If the supply chain wheels begin to spin for HJT, it is just a matter of scaling up. We see this in wafer supplies; the price gap between n- and p-type M2 wafers keeps shrinking.

How do you develop the trust with your potential partners to convince them to adopt HJT and SmartWire Connection technology? What conversations are you having?

At the beginning of the year we critically reviewed the HJT launch strategy and implemented quite a few changes on how to approach the market. In the past, the HJT strategy focused on only selling complete lines. If people had asked for just a HELiA tool or only a SmartWire system to either produce modules on their existing module lines or source their HJT cells from elsewhere, we would not have readily considered that request as we were focusing on selling complete cell and module lines. Now we have adjusted our market approach to offer flexible HJT core equipment and integrated production lines. Customers tell us what their requirements are and we aim to deliver the solution.

We believe the combination of HJT and SWCT is ideal, but we won’t be the missionary for this technology. Customers make decisions rationally, and we will support them accordingly. This change in our market approach has been successful for us; the whole topic has much stronger traction today. It also convinces customers that we operate a HJT production line at Meyer Burger in Germany. Upon customer request, we have the immediate ability to show them our HJT production tools in operation, including compelling efficiency, availability and yield data. We can show to customers that what we produce is real, and we operate at yields that are getting very close or even in-line to the current global best-in-class average.

The HJT maturity level at Meyer Burger is higher than it has ever been. In fact, I don’t know of any other cell technology that was tested and industrialized so thoroughly in order to prepare a smooth adoption in the industry. In our opinion, this is important because we have to recognize that the industry is very risk averse: customers need tangible proof that what we say is real and not just a number in a PowerPoint presentation.

What is the outcome for a manufacturer to pair the HJT/SWCT combination work with glass-glass encapsulation?

SWCT works with both glass-glass and glass-backsheet module designs. Glass-glass has a huge advantage in that it helps to use the bifaciality of the solar cells and reduces the silver use significantly. Glass-glass also enables a much longer product lifetime, enabling a manufacturer to increase product yield guarantees up from 20 or 25 years to 30 years, and in the long run maybe more. If you put a cell matrix into a symmetric glass-glass laminate, this creates a zero-force lamellae, where the cell matrix is positioned and the cells are unlikely to be damaged. This allows the use of thin wafers of <150 µm thickness. Thin wafers and less paste lay-down reduces the material costs for the two most expensive cost drivers in the solar supply chain – silicon and silver – while the glass-glass sandwich offers more stability and longer product life.

Another unique advantage of SWCT is the low temperature soldering, with a very cost-effective soldering alloy. Originally the soldering material was costly, and Meyer Burger has been able to adapt it successfully. The low temperature soldering provides a low thermal stress process, and here we see a clear advantage compared to other multi wire technologies. This is in addition to the fact that glass-glass is already contributing to the extended lifetime and lower degradation.

How much competition is there from Chinese equipment providers on busbarless cell interconnection technologies such as SmartWire?

Fair competition is good for business. Always. It means companies question themselves and try to improve their product offering. We are not concerned about competition, but we take it seriously, as we should. We can say that Chinese competitors are getting more traction, getting more up to speed and understanding how to position themselves in the industry. Meyer Burger annually invests around 10% of its net sales in R&D and continues to offer a unique technological proposition; our MAiA machine is an example of how we could help change and drive the market on the PERC side.

On HJT, yes there are other players in the world offering HJT equipment, but the fact we have been able to industrialize the processes and equipment achieving 24.02% best cell efficiency and 335 W module power with standard production equipment makes us unique. For modules, the standard busbar business is very much in the hands of Asian companies, and this was addressed in our announcement in November the we plan to discontinue busbar production, which is a commodity that is currently handled by mainly Asian companies with just a few remaining in the west.

So Meyer Burger is looking ahead. We have a clear target – set by the solar industry and not only set by ourselves: and that is strong need for higher module power at lowest manufacturing costs, for less or no power degradation both resulting in a better LCOE cost structure. Another target set by the industry is that the module technology has to trend towards multi-busbar. SmartWire is a way to reduce the optical and ohmic resistance losses in the solar module, and to better leverage higher cell power – either by using SWCT for HJT or SWCT for PERC and PERT cells. SmartWire has many advantages over alternative wire technologies where the soldering is still done the “old” way, thus creating a lot of mechanical stress: we can avoid all of this with our patented SWCT technology.

We have concepts in the works for higher productivity per tool to cope with increased overall equipment efficiency. And again, fair competition is helpful to make our performance better. With the SWCT technology we are currently working on, we believe we are well positioned to corner a big share of the market, and continue to set PV industry standards.

Ian Clover

Ian joined the pv magazine team in 2013 and specializes in power electronics (inverters) and battery storage. Ian also reports on the UK solar market, having worked as a print and web journalist in Britain for various multimedia companies, covering topics ranging from renewable energy and sustainability to real estate, sport and film.More articles from Ian Clover

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